1. Field of the Invention
The present invention relates to a tile suitable for use on a variety of surfaces including walls, roofs or other defined areas. The tile is translucent or transparent to solar energy and, in direct conjunction with the underlying surface, provides a conduction path for an energy transfer fluid heated by solar energy effects on the underlying surface.
2. Description of the Related Art
Various elements for incorporation with solar energy collection systems have been developed in an effort to provide a solar energy collection system that can be placed on and, to some extent, blend in with a surrounding surface structure. Each of the designs have a number of disadvantages.
For example, U.S. Pat. No. 4,083,360 to Courvoisier et al. describes the use of transparent tiles to allow solar energy to pass through to an underlying solar energy absorbing plate. The tile is designed to resist precipitation and provide additional insulation above the absorbing plate. The tiles, however, do not themselves form a mechanism for collecting the heat from the absorbing plate and conducting it away for use. In fact, the tiles are specifically designed to prevent the motion of a solar energy transfer fluid, such as air, along their length. They also do not form an entire roof structure but rather only provide covering for the area of the discrete solar energy absorbing plates.
U.S. Pat. Nos. 4,953,537 and 5,022,381 to Allegro describe a roofing element with a transparent top surface and a closed conduit segment, internal to the tile, for carrying a heat absorbing fluid and for connecting to other like closed conduit segments in adjacent tiles. Such roofing elements require substantial amounts of material and relatively complicated fabrication techniques. Further, when properly interconnected the roofing elements collectively provide a closed internal conduit for the heat exchange fluid. Additionally, they do not use all of the solar energy falling on the roof due to the reduced areas available for transmission and absorption of solar energy in order to provide areas for fastening the elements to the roof and for overlapping mating edges. If used as the primary shingling of the roof, the elements require glue or tar as a sealant.
A number of patents disclose hollow, box-like elements having couplings for connecting each element to adjacent elements to provide a continuous fluid flow path between the elements. For example, U.S. Pat. No. 4,428,360 to Cohen describes a shingle system in which individual shingles have top and bottom plates which are seamed to form a closed cavity therebetween for containing a fluid that is heated by solar energy. Individual shingles also have fluid inlet and outlet couplings for connecting each shingle in open flow communication with surrounding shingles. U.S. Pat. No. 4,359,043 to Dominique et al. describes a roofing member with top and bottom plates forming a closed cavity therebetween for containing a heat absorbing fluid. Tubular conduit segments project from the top plate and extend into a cavity in the bottom plate of an adjacent, overlapping roofing member to form a passageway to allow the heat absorbing fluid to flow from one member to an adjacent member. U.S. Pat. Nos. 4,428,361 and 4,244,353 to Straza describe a solar heating shingle comprising a flat hollow body of the same general size and configuration as a conventional shingle with fluid inlets and outlets. The inlets and outlets of longitudinally overlapping shingles are connected to effectively create a closed path for the flow of a heat exchanging fluid. All these shingles or roofing elements are complex to fabricate and install due to the double walled construction and the need to properly interconnect adjacent members to form the closed fluid path. The elements also require additional material and components to provide the bottom plate and fluid couplings, restrict fluid flow through the interconnecting fittings, and suffer stresses from repeated cycles of thermal expansion and contraction at the fittings which tend to separate or wear out the connections for the flow of heat transfer fluid.
U.S. Pat. Nos. 4,284,065 and 4,405,396 to Brill-Edwards describe roofing panels with rows of longitudinal corrugations that simulate rows of conventional roofing tiles. The panels are fabricated with a matrix of closed channels therein for transmitting a heat exchange fluid. U.S. Pat. Nos. 4,278,071 and 4,382,435, also to Brill-Edwards, describe roofing panels with an outer skin and an inner liner spaced from the outer skin by longitudinal beams so as to form tunnels between the outer skin and the inner liner from the eaves of the roof to the crest. In both types of panels, the top surface of the panel is heated by solar energy and the heat exchange fluid is conducted up through the panel from the bottom to the top of the roof. The panels rely on the outer surface to absorb solar energy which can easily loose heat to the atmosphere above the panel. Furthermore, the panels require additional material because of the presence of the bottom surface and other structures and require complex fabrication and installation processes. Also, because the panels extend from the top to the bottom of the roof, they are not easily installed around or adapted to any protrusion through the roof such as chimneys, vent pipes, dormers, and other similar roofing obstacles.
U.S. Pat. No. 2,624,298 to Farren describes a solid, totally opaque roof tile with a lower end that is closed and longitudinal and lateral air passages integral to the bottom of the tile for promoting air circulation within the body of the roof. The design, however, incorporates several grooves and ribs in the bottom surface of the tile which restrict the flow of air compared to one large opening. No mention is made of an air passage for the purpose of ducting heat generated by solar energy, nor of constructing a tile that allows solar energy to pass through the tile to be absorbed by the surface material below the tile.
U.S. Pat. No. 4,967,729 to Okumura discloses a solar energy collector that comprises multi-layer panels including a metal top plate and a bottom plate constructed with a heat insulation layer and an airflow path defined therebetween. The upper plate is heated by solar energy and heat is conducted away by air in the airflow path that lies adjacent the top metal surface. Layers of glass placed over the metal plate toward the top of the roof act as a glazing that allow the metal plate thereunder to reach higher than ambient temperatures due to absorbed solar radiation because the glazing acts to prevent the loss of absorbed solar energy. The panels require additional material and more complex fabrication due to the use of top and bottom plates in the construction of the airflow path. Furthermore, because the panels extend from the top to the bottom of the roof, they are not easily installed around or adapted to any protrusion through the roof such as chimneys, vent pipes, or dormers. In addition, the heated air between the glass plates and the metal top plate is not collected for use. Finally, the unglazed portion of the metal top plate at the lower portion of the roof can loose substantial energy to the atmosphere.
Finally, U.S. Pat. No. 4,299,201 to Tsubota discloses a Spanish-style tile having multiple fine menisci on its inner surface to focus incident sunlight onto a solar energy conversion device, such as a pipe with a heat transfer fluid flowing therethrough, disposed within the open area beneath the tile. The energy conversion device disclosed is a closed system for conducting a solar energy collecting fluid. The fabrication of this device would be complex and would require additional components to provide for the solar energy conversion device. Furthermore, solar energy passing through the tile surface from many angles will not be focused on the solar energy conversion device but will strike the surrounding roof surface and be wasted because the heated air beneath the tile is not collected for use. The resulting buildup of heat beneath the tile will also result in larger energy losses to the surroundings.
As can be seen, there remains a need for surface covering tiles that can transmit, by radiation, all solar energy impinging upon the surface area covered by the tiles to an underlying surface to be absorbed thereby so that an energy transfer fluid moving directly between the interior of the tile and the underlying surface will be heated and conducted within an open fluid flow path between the tile and the surface on which it is mounted. The tile should be of simple fabrication, require minimum material, and be as easily installed as conventional tiles. Employed as a roofing tile, such a surface covering tile would not require additional or customized roof construction, would allow the entire surface area of the roof to be used as a solar collection surface, would maintain the geometric appearance of conventional clay or cement roofing tiles, and could be used on virtually any shape or type of sloped roof design. Further, the energy absorbing underlying surface can be a source of color, with the integrity of the color being protected from weathering effects.